Hinging devices for seat backs

Abstract

The invention relates to a seat back hinge comprising a control handle, an inner toothed ring integral with the side-plate of the sitting portion, an inner toothed ring integral with the side-plate of the seat back and toothed bolts adapted to coact with these rings, these bolts being able to be moved radially under the action of a rotary cam integral with the handle and being mounted transversely floating as well as said cam. The side-plates and the cam are mutually centered by cooperation on the one hand of a cylindrical projection of the cam with a bore of one of the side-plates and, on the other hand, of a cylindrical bore of the cam with a projection of the other side-plate.

We claim: 
     
       1. A seat back hinging device comprising: a control handle accessible to the person sitting in the seat;   a first inner toothed ring integral with a side-plate of the sitting portion of the seats   a second inner toothed ring integral with a side-plate of the seat back portion and coaxial with said first ring;   locking means actuable by the control handle to responsively cause said first and second rings to be either angularly locked or angularly free with respect to one another; said locking means comprising n toothed bolts each adapted to coact with the teeth of said first and second rings, said bolts being spaced apart evenly about the common axis of these rings interiorly thereof, at respective mutual angular distances of the other of 360°/n, n being a whole number at least equal to 1, and a central rotary flat cam actuable by said control handle and adapted to coact with said bolts so as either to move them radially away from said common axis to put them in locking relationship with said first and second rings, or to cause them to move radially nearer said common axis thereby freeing them from said locking relationship; and   means for resiliently urging the control handle and the cam towards their position corresponding to said locking relationship, the bolts and the cam being mounted so as to be able to float slightly transversely with respect to said first and second side-plates while being wedged axially therebetween, said hinging devide further characterized in that the rotary flat cam includes a first cylindrical projection on one of its faces adapted to coact with a first complementary bore in one of said side-plates, said first projection and bore defining a first clearance therebetween and, on its other face, a second cylindrical bore adapted to coact with a second complementary projection on the other of said side-plates defining therebetween a second clearance so that said first and second coacting projections and bores assist in the relative centering of said side-plates.   
     
     
       2. The hinging device as claimed in claim 1, characterized in that the projection and the bore of the cam correspond, having been obtained simultaneously by semi-cutting out. 
     
     
       3. The hinging device as in claims 1 or 2 wherein the number and orientation of the teeth on said first and second toothed rings are identical. 
     
     
       4. The hinging device as in claims 1 or 2, wherein each of the clearances defined between a coacting bore and projection is about 0.1 mm. 
     
     
       5. The hinging device as in claim 4 wherein the number and orientation of the teeth on said first and second toothed rings are identical. 
     
     
       6. The hinging device as in claim 4 wherein each of the bolts cooperates with a radial guide integral with one of the side-plates, said guide and at least one edge of its respective cooperating bolt defining a clearance of about 0.2 mm. 
     
     
       7. The hinging device as in claim 6 wherein the number and orientation of the teeth on said first and second toothed rings are identical. 
     
     
       8. The hinging device as in claim 6 wherein said cam is welded to a stub shaft integral with the control handle. 
     
     
       9. The hinging device as in claim 8 wherein the number and orientation of the teeth on said first and second toothed rings are identical. 
     
     
       10. The hinging device as in claim 6 wherein said cam is integral with a stub shaft passing freely through an opening provided in the side-plate having said second projection. 
     
     
       11. The hinging device as in claim 10 wherein the number and orientation of the teeth on said first and second toothed rings are identical.